U.S. Patent Application Publication No. 200/0032275A1 published Feb. 10, 2011, Gabriel G. Marcu, et al., incorporated herein by reference in its entirety, is directed to performing corrections on video data based on the temperature of a video display to produce accurate output values on the display. As explained there, many computing devices, television sets, etc. use an electronic display, such as liquid crystal displays, cathode ray tubes, and organic light emitting diode displays. Typically, such displays show color images, but that is not limiting here. The color response of such displays typically changes as the display operates and particularly as it warms up after being powered up.
As explained there, “white point” (correlated color temperature) shifts along a black body curve as a physical temperature of the display reaches its steady operating temperature. So there is a color shift over time as the display warms up, referred to also as transient color shift. The transient color shift is noticeable often for a quite lengthy period of time, such as up to 2 of 3 hours. This is also the case even if the display is only a black and white display, that is displays only “gray scale”. Other parameters of the display may similarly shift as a function of temperature such as luminance, black level, contrast, or the electro-optical transfer function referred to as the “gamma”.
The target white point, also referred to as target white, is a set of values that served to define the desired color white for a particular image. Different definitions of target white are needed to give particular optical results. The white point of the display refers to the color that is produced by the display as a response to the maximum digital input on all 3 color channels.
A white point correction refers to a video signal correction that changes the white point of a display to match a target white point.
The target gamma refers to a certain luminance response of the display to the digital input. Target gamma correction typically follows the power law (is an exponential function). Gamma correction is used to encode RGB (red, green, blue) values of the video signals or digital values such that the display response is luminance to the digital input matches the input on all 3 color channels.
However, even the particular correction disclosed in that patent publication can be improved upon, as identified by the present inventors and described following.